Fault indicating means



Patented Apr. 15, 1941 FAULT INDICATIN G MEANS Edmund O. Schweitzer,Jr., North Brook, Ill.

Original application August 11, 1939, Serial No.

289,600, now Patent No. 22,224,320, dated December 10, 1940. Divided andthis application August 21, 1940, Serial N0. 353,468

7 Claims.

power distribution system. This application, is4

a division of my copending application, Serial No. 289,600, filed August11, 1939, now Patent No. 2,224,320.

An object of my invention is to detect the ow of unbalanced current in acircuit in which the current ow is normally balanced by measuring onlythe unbalanced current flow. Y

Another object of my invention is to balance the magnetomotive forcesincident to normal current ow in an electric circuit and to measure onlythe unbalanced magnetomotive forces which are set up under faultconditions when unbalanced current ilow takes place.

Other objects of my invention will, in part, bc

obvious and, in part appear hereinafter. My invention, accordingly, isdisclosed in the embodiments thereof shown in the accompanying drawing,and it comprises Ithe features of construction, combination of elementsand arrangement of parts which will be exemplified in the constructionshereinafter set forth, and the scope of the application of which will beindicated in the appended claims.

For a more complete understanding of the nature and scope of myinvention, reference may be had to the following detailed descriptiontaken in connection with the accompanying drawing, in which:

Figure 1 illustrates diagrammatically how my invention may be employedto detect the occurrence of a fault between the windings of a currentsource and ground and also between a, line conductor and ground; and 1Figures 2 and 3 illustrate diagrammatically how my invention may beemployed in connection with different arrangements of polyphasecircuits. Referring now to Figure 1 of the drawing, it will be observedthat conductors 3|, 32 and 33 represent a single phase 3-wire systemthat may be connected by switches 34 to a suitable load circuit. Theconductors are energized from a transformer, shown generally at 35,having a secondary Winding 36 that is connected to the conductors 3| and33 and has a center tap 3l which is connected to the conductor 32. Thetransformer 35 is provided with a primary winding 38 Y that is connectedfor energization across a source 33 of alternating current, such as aSil-cycle source, 'Ihe transformer 35 is provided with a core which isindicated at 40 and which is connected to a ground conductor 4| thatparallels e the conductors 3|, 32 and 33 and is connected by a conductor42 to the conductor 32.

Assuming now that it is desirable to provide an instantaneous indicationof a failure, as indicated at 43 between some of the turns of thesecondary winding 36 of the transformer 35 and the core 40 or ground, 'amagnetic core 44 is provided which completely encircles the conductors3|, 32 and 33. While these conductors are shown, for illustrativepurposes, as being spaced relatively far apart,'it will be understoodthat the distances between the conductors 3|, 32 and 33 are relativelysmall as compared to the distances between them and the magnetic core44.

Under normal operating conditions the fault as indicated at 43 does notexist and the same amount of current that flows outwardly through theconductors 3|, 32 and 33 within the core 44 also flows back.Consequently, the magnetomotive forces with respect to the magnetic core44 are balanced and no flux iiows through it. Upon the occurrence of thefault a-t 43 some current flows through the conductor 4| andconsequently the magnetomotive forces applied to the magnetic core 44are unbalanced and as a result a voltage is induced in the winding 45thereon.

The presence o-f this voltage then indicates that a fault has occurredand it may be utilized, as will readily be understood, for disconnectingthe conductors 3|, 32 and 33 and the transformer 35 from the source 39in a manner such as is clis-l closed in the application of which thisapplication is a division.

Now assuming that a fault occurs, as indicated at 46, between theconductor 33 Iand the ground conductor 4| or, as indicated at 4l,between the switch 34 and this ground conductor, which may happen onopening of the switch, there would be no Voltage induced in the winding45 on the magnetic core 44 because the magnetomotive forces would bebalanced. To take care of this fault condition another magnetic core 48is provided around the conductors 3|, 32 and 33 with the connection ofthe ground conductor 4| to the conductor 32 being between it and theother magnetic core 44 A winding 43 is provided, as shown, on themagnetic core 48. On the occurrence of either of the faults, asindicated at 4B or 41, the magnetomotive forces applied to the magneticcore 48 will become unbalanced and, as described, a voltage will beinduced in the winding 43 which may operate means as describedforwinding 45.

While, for illustrative purposes, the windings 45 and 49 are shown asbeing positioned slightly phase protection in Figure 1.

ings 86 which are connected for energization to a 3-phase, starconnected, grounded neutral generator 'shown diagrammatioally at 81. Thetransformer 85 is provided with a. core 88 and .star connected secondarywindings 89, the neutral point of which is connected to a groundconductor 90. Circuit conductors 9|, 92 and 93 are connected, as shown,to the windings 89.

With a view to indicating the occurrence of a fault, such as the fault94 between one'of the windings 89 and the core 88 of the transformer 85or to ground, a magnetic core 95 is provided surrounding all of theconductors 99, 9|, 92 and 93, which, it will be understood, arepositioned in insulated spaced relationship with the distances .Y

between them being relatively small as compared to the distances betweenthem and the magnetic core 95. A winding 96 is provided on the core 95and a voltage will be induced in it on the occurrence of the fault 94,as will now be readily understood.

On the occurrence of a fault, such as indicated at 91, constituting ashort circuit to ground from the line conductor 92, therev would be novoltage induced in the Winding 96 because the magnetomotive forcesapplied to the core 95 would remain balanced. In order to take care ofkthis fault condition, a core 98 is provided around the conductors 99,9|, 92 and 93 and a winding 99 is positioned thereon. A voltage will beinduced in the winding 99 on the occurrence of a fault, such as thefault 91.

Windings 96 and 99 can be connected to suitable means, such as disclosedin the application of which this application is a division, for open ingthe circuit to clear the fault.

In Figure 3 of the drawing, the conductors 90, 9|, 92 and 93 areconnected directly to the 3- phase generator 81 without the`interposition of the transformer 85. 81 is indicated at |88 and,assuming that a fault occurs, as indicated at Illl, between one of the`generator windings and the core |00 or ground, then it will heunderstood that a voltage will be induced in the winding 96 which willindicate the presence of this fault. While the conductor 90 is shown aspassing through the magnetic core 95, it will be observed that it doesnot pass through the magnetic core 98. In the event that the currentflow in the conductors 9|, 92 and 93 becomes unbalanced so that there iscurrent ow in the neutral conductor 99, then the balanced magnetomotiveforces will no longer exist and a voltage will be induced in the winding99. The balanced condition of the magnetomotive forces will also beupset in the event that there should occur a fault between one of theconductors 9|, 92 or 93 and the ground conductor 99 or ground.

Since certain further changes can be made in the above constructions anddifferent embodiments of the invention can be made without departingfrom the scope thereof, it is intended that all matter contained in theforegoing der scription or shown in the accompanying drawing The core ofthe generator shall be interpreted as illustrative and not in a limitingsense.

I claim as my invention:

1. In an electric power distribution system, in combination, a core, awinding on said core ener- `ized with alternating current, a loadcircuit connected across said winding, said core and one conductor ofsaid load circuit being grounded, a magnetic circuit surrounding saidload circuit into which flux is induced on the occurrence of a shortcircuit between said winding and said core, the distance between theconductors forming said load circuit being relatively small as comparedto the distance between said conductors and said magnetic circuit, andmeans linking said magnetic circuit and responsive to said ux inducedtherein.

2. In an electricA power distribution system, in combination, a core, awinding on said core energized with alternating current, a load circuitconnected across said winding, said core and one conductor of said loadcircuit being grounded, a magnetic circuit surrounding said loadcircuit, the distance between the conductors forming said load circuitbeing relatively small as compared to the distance between saidconductors and said magnetic circuit, the ground on said one conductorbeing between said winding and said magnetic circuit whereby ux isinduced in the latter only on iiow of short circuit current in said loadcircuit to ground beyond said magnetic circuit, and means 'linking saidmagnetic circuit and rei sponsive to said flux induced therein. v

3. In an electric power distribution system, in combination, a core, awinding on said core energized With alternating current, a load circuitconnected across said winding, said core and one conductor of said loadcircuit being grounded, a magnetic circuit surrounding said load circuitinto which flux is induced on the occurrence of a short circuit betweensaid winding and said core, another magnetic circuit surrounding saidload circuit, the distance between the conductors forming said loadcircuit being relatively small as compared to the distance between saidconductors and said magnetic circuits, the ground on said one conductorbeing between said lmagnetic circuits whereby flux is induced in saidother magnetic circuit only on flow of short circuit current in saidload circuit to ground beyond said other magnetic circuit, and windingmeans linking said magnetic circuits in which a voltage or voltages aregenerated as a result of induction of flux in said magnetic circuits onilow of short circuit current on the occurrence of either or both of thetances between said conductors and said magnetic circuit, and meanslinking said magnetic circuit and responsive to said flux inducedtherein.

' 5. In an electric power distribution system, in combination, coremeans, windings on said core means energized with polyphase alternatingcurrent, a load circuit including a plurality of line conductors and aneutral conductor connected to said windings, said core and neutralconductor being grounded, a magnetic circuit surrounding said loadcircuit, the distances between the conductors forming said load circuitbeing relatively small as compared to the distances between saidconductors and said magnetic circuit, the ground on said neutralconductor being between said said load circuit into which flux isinduced on they occurrence of a short circuit between any of saidwindings and said core means, another magnetic circuit surrounding saidload circuit, the distances between the conductors forming said loadcircuit being relatively small as compared to the distances between saidconductors and saidmagnetic circuits, the ground on said neutralconductor being between said magnetic circuits whereby flux is inducedinto said other magnetic circuit only on flow of short circuit currentin said load circuit to ground beyond said other magnetic circuit, andwinding means: linking said magnetic circuits in which a voltage orvoltages are generated as a result of induction of flux in said magneticcircuits on flow of short circuit current on the occurrence of either orboth of the aforesaid fault conditions.

7. In an electric power distribution system, in combination, core means,windings on said core means energized with polyphase alternatingcurrent, a load circuit including a plurality of line conducto-rs and aneutral conductor connected to said windings, said core and neutralconductor being grounded, a magnetic circuit surrounding said lineconductors into which flux is induced on the occurrence of unbalancedcurrent flow in said line conductors, the distances between said lineconductors being relatively small as compared to the distances betweensaid line conductors and said magnetic circuit, and means linking saidmagnetic circuit and responsive to said flux induced therein.

EDMUND O. SCHWEITZER, JR.

